A kind of power battery internal multiple physical quantity optical fiber sensing device and monitoring method

Abstract

The application provides a power battery internal multi-physical quantity optical fiber sensing device and a monitoring method, relates to the technical field of lithium battery state monitoring, and comprises the following: a light source; a polarization controller used for converting initial light into linearly polarized light with a preset angle and transmitting the linearly polarized light to a first port of a fiber optic circulator; the fiber optic circulator is used for unidirectionally transmitting the linearly polarized light to a multi-quantity optical fiber sensor and unidirectionally transmitting interference signal light reflected back to a spectrum analyzer; the multi-quantity optical fiber sensor comprises a fiber grating and a seven-core optical fiber, the fiber grating is fused with the seven-core optical fiber, a palladium-gold composite film is arranged on the end face of the seven-core optical fiber away from the fiber grating, and the palladium-gold composite film is immersed in a medium to be measured; the spectrum analyzer is used for collecting reflected light spectrum according to the interference signal light, and determining the measurement temperature, the measurement stress and the measurement hydrogen concentration of a measurement interface of the power battery according to the reflected light spectrum. The application can realize the synchronous monitoring of the temperature, the stress and the hydrogen concentration.

Description

Technical Field

[0001] This application relates to the field of lithium battery state monitoring technology, and in particular to a fiber optic sensing device and monitoring method for multiple physical quantities inside a power battery. Background Technology

[0002] Lithium-ion batteries play a crucial role in electric vehicles and large-scale energy storage. However, the high activity of the electrodes and the flammability of the electrolyte pose significant safety risks. These safety hazards can ultimately lead to thermal runaway. When thermal runaway occurs in a lithium-ion battery, the violent combustion and explosion are extremely dangerous. This has become one of the greatest challenges facing lithium-ion batteries.

[0003] The initiation point and earliest trigger location of thermal runaway are highly concentrated at the interface between the separator and the negative electrode. When the battery experiences a localized temperature increase due to overcharging, overheating, or an internal short circuit, the SEI (solid electrolyte interface) film on the negative electrode surface will decompose first, releasing heat and generating a large amount of flammable gas (including hydrogen). This reaction only occurs at the interface where the negative electrode active material is in direct contact with the electrolyte, and since the separator is the structure closely attached to the negative electrode, the separator-negative electrode interface becomes the earliest starting point of the thermal runaway chain reaction. Subsequently, the SEI film ruptures, causing the exposed negative electrode to react violently with the electrolyte, further releasing gas and heat; the temperature continues to rise, causing the separator to shrink and melt, ultimately triggering a direct short circuit between the positive and negative electrodes, resulting in explosive thermal runaway.

[0004] Fiber optic monitoring offers higher precision and sensitivity, and is unaffected by electromagnetic interference. It can accurately capture subtle temperature fluctuations and strain changes in lithium-ion battery parameters, ensuring the accuracy, continuity, and durability of monitoring data. Real-time monitoring of lithium-ion batteries using high-precision, high-sensitivity technology allows for timely detection of abnormal batteries, preventing thermal runaway, which is crucial for improving lithium-ion battery safety. Current technologies generally focus on the independent monitoring of single or a few parameters. The limitations of this monitoring approach make it difficult to comprehensively reflect the multi-physics coupling state of the battery cell under complex operating conditions, easily leading to inaccurate state assessments and increasing the risk of misjudgments or missed alarms in early warning systems. Summary of the Invention

[0005] In view of this, this application proposes a fiber optic sensing device and monitoring method for multiple physical quantities inside a power battery.

[0006] In a first aspect, this application provides a multi-physical quantity fiber optic sensing device for a power battery, including: a light source, a polarization controller, a fiber optic circulator, a multi-parameter fiber optic sensor, and a spectrometer. The light source is used to output initial light to the polarization controller; The polarization controller is used to convert the initial light into linearly polarized light at a preset angle and transmit the linearly polarized light to the first port of the fiber optic circulator; The second port of the fiber optic circulator is connected to the multi-parameter fiber optic sensor, and the third port of the fiber optic circulator is connected to the spectrometer. The fiber optic circulator is used to transmit the linearly polarized light unidirectionally from the first port to the second port, and to transmit the interference signal light reflected back by the multi-parameter fiber optic sensor unidirectionally from the second port to the third port. The multi-parameter fiber optic sensor includes a fiber optic grating and a seven-core fiber. The first end of the fiber optic grating is connected to the second port. The first end of the seven-core fiber is fused to the second end of the fiber optic grating. A palladium-gold composite film is disposed on the end face of the second end of the seven-core fiber. The end face of the second end of the seven-core fiber is immersed in the medium to be measured. The spectrometer is used to collect the reflection spectrum based on the interference signal light, and to determine the measurement temperature, measurement stress, and measurement hydrogen concentration at the power battery measurement interface based on the reflection spectrum.

[0007] In one embodiment, the palladium-gold composite film comprises: a gold film layer and a palladium film layer stacked together; The gold film layer is located on the end face of the second end of the seven-core optical fiber, and the palladium film layer is located on the side of the gold film layer away from the seven-core optical fiber.

[0008] In one embodiment, the thickness of the gold film layer ranges from 10 to 12 nm, and the thickness of the palladium film layer ranges from 8 to 15 nm.

[0009] In one embodiment, the seven-core optical fiber includes a central core and six peripheral cores. The spacing between the cores in the seven-core optical fiber is 10–12 μm, and the diameter of the central core and the six peripheral cores is 8–10 μm. The six peripheral cores are arranged in a hexagonal symmetrical pattern.

[0010] In one embodiment, the fiber grating is a single-mode fiber, and the single-mode fiber is aligned with the central fiber core.

[0011] In one embodiment, the multi-parameter fiber optic sensor further includes an insulating encapsulation layer for encapsulating the fiber grating and the seven-core fiber, and leaving an exposure window for the palladium composite film at the second end of the seven-core fiber.

[0012] In one embodiment, the spectrometer is further used to collect amplitude data and wavelength drift data at the target wavelength in the reflection spectrum, and to determine the temperature, stress and hydrogen concentration of the power battery measurement interface based on the amplitude data and wavelength drift data at the target wavelength, wherein the wavelength range of the target wavelength is 1550-1600nm.

[0013] In one embodiment, the end face of the second end of the seven-core optical fiber is a single-reflection end face.

[0014] Secondly, this application also provides a method for monitoring multiple physical quantities inside a power battery, wherein the method is performed based on the fiber optic sensing device for multiple physical quantities inside a power battery as described in the first aspect; the method includes: The reflection spectrum is preprocessed to extract wavelength data at the target wavelength. The wavelength data includes the overall wavelength drift data of the seven-core fiber supermode interference spectrum, the wavelength drift data of the Bragg reflection peak, and the amplitude data at the target wavelength. Obtain the 3×3 sensitivity matrix calibrated under standard operating conditions, wherein the standard operating conditions are constant temperature, no strain, and hydrogen-free environment. The measurement temperature is determined based on the 3×3 sensitivity matrix, baseline temperature, and overall wavelength drift data of the seven-core fiber supermode interferometry spectrum. The measurement strain is determined based on the 3×3 sensitivity matrix, baseline strain, and wavelength drift data of the Bragg reflection peak. The measurement hydrogen concentration is determined based on the 3×3 sensitivity matrix, baseline hydrogen concentration, and amplitude data at the target wavelength.

[0015] In one embodiment, the method for monitoring multiple physical quantities inside the power battery further includes: The temperature reference value, strain reference value, and hydrogen concentration reference value used to calibrate the normal operation of the battery are respectively used as the baseline temperature, baseline strain, and baseline hydrogen concentration; Determine the deviations of the measured temperature, the measured stress, and the measured hydrogen concentration from the corresponding reference values; The anomaly level of each physical quantity is determined based on the deviation, and the thermal runaway risk level of the measured power battery is determined based on the anomaly level of each physical quantity.

[0016] The fiber optic sensing device for multiple physical quantities inside a power battery disclosed in this application has the following advantages over related technologies: 1. The multi-physical quantity fiber optic sensing device inside the power battery of this application includes a light source, a polarization controller, a fiber optic circulator, a multi-parameter fiber optic sensor, and a spectrometer. The light source, polarization controller, and circulator form a series-connected all-fiber optical path. The polarization-normalization processing, combined with the unidirectional light-guiding characteristic of the circulator, can reduce optical path transmission loss, isolate electromagnetic interference inside the battery, and achieve split transmission of incident light and reflected signal light, ensuring stable incident light input and complete acquisition of reflected interference light, thereby improving the accuracy of spectral acquisition. Moreover, the multi-parameter fiber optic sensor, as the sensing end, does not require power and is immune to strong electromagnetic interference and high-voltage environment inside the battery. Parameter detection based on changes in optical refractive index is also unaffected by fluctuations in the electrochemical environment.

[0017] 2. Multi-parameter fiber optic sensors, comprising fiber optic gratings and seven-core fibers, utilize the strong coupling between the central core and six peripheral cores to stably excite and propagate two supermodes with significantly different effective refractive indices. Combined with the narrowband reflection peaks of fiber Bragg gratings (FBGs), a single reflection spectrum can simultaneously carry independent response information for multiple physical quantities. Temperature changes primarily cause an overall wavelength shift in the supermode interference spectrum, while strain changes affect both the FBG wavelength and the interference spectrum amplitude. The selective adsorption of hydrogen by the Au / Pd composite film at the end face specifically modulates the reflectivity and significantly affects the amplitude, having minimal impact on wavelength shift. Based on these characteristics, the spectrometer can acquire the reflection spectrum based on the interference signal light. According to this reflection spectrum, crosstalk-free linear decoupling of the three parameters—temperature, stress, and hydrogen concentration—can be achieved, enabling real-time, synchronous, and in-situ monitoring of temperature, stress, and hydrogen concentration. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a multi-physical quantity fiber optic sensing device inside a power battery in one embodiment of this application; Figure 2 This is a schematic diagram of the structure of a multi-parameter fiber optic sensor in one embodiment of this application; Figure 3 This is a flowchart illustrating a method for monitoring multiple physical quantities inside a power battery according to one embodiment of this application.

[0020] Explanation of reference numerals in the attached figures: 1-Light source, 2-Polarization controller, 3-Fiber optic circulator, 4-Multi-parameter fiber optic sensor, 41-Fiber grating, 42-Seven-core fiber, 43-Palladium-gold composite film, 431-Gold film layer, 432-Palladium film layer, 44-Insulating encapsulation layer, 5-Spectrometer, 6-Power battery. Detailed Implementation

[0021] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] In some embodiments, such as Figure 1 and Figure 2 As shown, this application provides a multi-physical quantity fiber optic sensing device for a power battery, comprising: a light source 1, a polarization controller 2, a fiber optic circulator 3, a multi-parameter fiber optic sensor 4, and a spectrometer 5.

[0023] Light source 1 is used to output initial light to polarization controller 2. Light source 1 can be a supercontinuum light source 1.

[0024] The polarization controller 2 is used to convert the initial light into linearly polarized light at a preset angle and transmit the linearly polarized light to the first port of the fiber optic circulator 3.

[0025] The second port of the fiber optic circulator 3 is connected to the multi-parameter fiber optic sensor 4, and the third port of the fiber optic circulator 3 is connected to the spectrometer 5. The fiber optic circulator 3 is used to transmit linearly polarized light unidirectionally from the first port to the second port, and to transmit the interference signal light reflected back from the multi-parameter fiber optic sensor 4 unidirectionally from the second port to the third port.

[0026] The multi-parameter fiber optic sensor 4 includes a fiber optic grating 41 and a seven-core fiber 42. The first end of the fiber optic grating 41 is connected to the second port, and the first end of the seven-core fiber 42 is fused to the second end of the fiber optic grating 41. A palladium-gold composite film 43 is disposed on the end face of the second end of the seven-core fiber 42, and the end face of the second end of the seven-core fiber 42 is immersed in the medium to be measured. The end face of the second end of the seven-core fiber 42 is a single-reflection end face. Based on this, the second end of the seven-core fiber 42 relies solely on the palladium-gold composite film 43 on this end face to achieve beam reflection, without any other reflective structures introducing stray reflection signals. After the incident light is transmitted to the end face, it is reflected by the composite film to form a supermode interference spectrum. The single reflective surface simplifies the spectral waveform and reduces interference from redundant optical signals.

[0027] The spectrometer 5 is used to collect the reflection spectrum based on the interference signal light, and to determine the measurement temperature, measurement stress and measurement hydrogen concentration of the power battery 6 measurement interface based on the reflection spectrum.

[0028] In the application, the output pigtail of light source 1 can be connected to the input of polarization controller 2 via an FC / APC connector. Polarization controller 2 performs polarization control on the initial light with disordered polarization, normalizing it into linearly polarized light with a fixed angle. This ensures stable excitation of the supermode interference effect by the seven-core fiber 42 at the back end. After converting the light into linearly polarized light with a preset angle, the output pigtail of polarization controller 2 is directly connected to the first port of the optical circulator. The second port of the circulator can be connected to the multi-parameter fiber optic sensor 4 via an optical fiber. The interference signal light reflected from the multi-parameter fiber optic sensor 4 returns to the second port of the circulator and is directionally transmitted to the third port, achieving mutual isolation between the incident light source 1 optical path and the reflected signal optical path, avoiding interference from incident stray light on the reflected spectrum. Finally, it is sent to the spectrometer 5 for detection and recording via an optical fiber jumper, effectively improving the quality of spectral acquisition and the accuracy of subsequent multi-physical quantity calculations. The entire optical path can be connected via fiber optic fusion splices or movable connectors to form a compact, low-loss reflective interferometry system.

[0029] The multi-parameter fiber optic sensor 4 comprises a fiber optic grating 41 and a seven-core fiber 42. A section of the seven-core fiber 42 can be fused with the fiber optic grating 41 to form the main structure. Then, a palladium (Au / Pd) composite film is functionalized on the second end face of the seven-core fiber 42. The core of this structure lies in the cascading of the fiber optic grating 41 and the seven-core fiber 42: utilizing the strong coupling characteristics between the central core and the six peripheral cores of the seven-core fiber 42, two supermodes with significantly different effective refractive indices are stably excited and propagated. Simultaneously, combined with the narrowband reflection peak of the FBG, a single reflection spectrum carries independent response information of multiple physical quantities. Temperature changes mainly cause an overall wavelength shift in the supermode interference spectrum, strain changes simultaneously affect the FBG wavelength and the interference spectrum amplitude, while the selective adsorption of hydrogen by the end-face Au / Pd composite film specifically modulates the reflectivity and significantly affects the amplitude, having minimal impact on the wavelength shift. This orthogonal response characteristic provides a solid physical foundation for subsequent crosstalk-free linear decoupling of the three parameters.

[0030] Moreover, the seven-core strongly coupled structure exhibits higher supermode difference and sensitivity compared to traditional two-core or three-core optical fibers, enabling the generation of clearer and more separable spectral characteristic responses. The single-reflection end-face Au / Pd composite film introduces chemically selective modulation of hydrogen within a very small volume, avoiding the volume increase and crosstalk risks associated with introducing additional independent gas sensing elements. Ultimately, this design enables real-time, synchronous, and in-situ monitoring of temperature, stress, and hydrogen concentration at the critical interface between the battery separator and the negative electrode using only a single reflection spectrum. It boasts extremely low invasiveness, millisecond-level decoupling response speed, and precise capture of the earliest trigger signal for thermal runaway, significantly outperforming traditional multi-fiber bundling or cascading schemes in terms of volume interference, decoupling complexity, and real-time monitoring performance.

[0031] Furthermore, the multi-parameter fiber optic sensor 4 in this embodiment adopts an integrated and miniaturized design, measuring a single point inside the battery. It integrates multiple types of sensitive structures within a limited space, making it suitable for detecting the local state of a critical interface within the battery. This addresses the problem of distributed fiber optic sensing devices being too bulky and occupying too much internal battery space. This low-intrusion characteristic is suitable for the confined and corrosive working environment inside the battery. Simultaneously, through multi-dimensional parameter collaborative analysis, it provides a more comprehensive assessment and early warning of the battery's actual operating state, significantly enhancing the reliability and accuracy of the battery safety early warning system.

[0032] The aforementioned power battery 6 contains a multi-physical quantity fiber optic sensing device, including a light source 1, a polarization controller 2, a fiber optic circulator 3, a multi-parameter fiber optic sensor 4, and a spectrometer 5. The light source 1, polarization controller 2, and circulator form a series-connected all-fiber optical path. The polarization-normalization processing, combined with the unidirectional light-guiding characteristic of the circulator, reduces optical path transmission loss, isolates electromagnetic interference inside the battery, and enables the separate transmission of incident and reflected signal light, ensuring stable incident light input and complete acquisition of reflected interference light, thus improving spectral acquisition accuracy. Moreover, the multi-parameter fiber optic sensor 4, as the sensing end, does not require power and is immune to strong electromagnetic interference and high-voltage environments inside the battery. It detects parameters based on changes in optical refractive index and is unaffected by fluctuations in the electrochemical environment. The multi-parameter fiber optic sensor 4 includes a fiber optic grating 41 and a seven-core fiber 42. By utilizing the central core and six peripheral cores of the seven-core fiber 42, and the cascaded characteristics of the aforementioned fiber optic grating 41 and the seven-core fiber 42, a solid physical foundation is provided for the subsequent realization of crosstalk-free linear decoupling of the three parameters. Finally, the spectrometer 5 can collect the reflection spectrum based on the interference signal light. According to the reflection spectrum, the three parameters of temperature, stress, and hydrogen concentration can be decoupled without crosstalk, thereby enabling real-time, synchronous, and in-situ monitoring of temperature, stress, and hydrogen concentration.

[0033] In some embodiments, such as Figure 2 As shown, the palladium-gold composite film 43 includes a gold film layer 431 and a palladium film layer 432 stacked together. The gold film layer 431 is located on the end face of the second end of the seven-core optical fiber 42, and the palladium film layer 432 is located on the side of the gold film layer 431 away from the seven-core optical fiber 42.

[0034] The gold film layer 431 has a thickness ranging from 10 to 12 nm, and the palladium film layer 432 has a thickness ranging from 8 to 15 nm. For example, the thickness of the gold film layer 431 can be 10 nm, 11 nm, or 12 nm, and the thickness of the palladium film layer 432 can be 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, or 15 nm. It should be noted that the above examples are only partial examples and do not constitute a limitation on the thickness of the gold film layer 431 and the palladium film layer 432. The gold film layer 431 is controlled at 10–12 nm and closely adheres to the fiber end face. This thickness can stably play a role in substrate reinforcement and ensure the basic reflection intensity of the end face. If the thickness is too thin, it is easy to have coating defects and excessive reflection loss. If it is too thick, it will hinder the light field from penetrating to the outer palladium film. The outer palladium film thickness is limited to 8–15 nm and directly contacts the electrolyte. The appropriate thickness can fully contact and adsorb hydrogen gas and sensitively change the film reflectivity, without increasing the volume of the fiber optic probe or hindering the penetration of hydrogen molecules due to excessive film thickness. The thickness parameters of the two film layers are coordinated to ensure that the palladium-gold composite film 43 balances optical reflection performance and hydrogen sensing sensitivity.

[0035] It is understandable that the palladium-gold composite film 43 is arranged in layers, with the inner gold film bonded to the end face of the second end of the seven-core optical fiber 42, and the palladium film stacked on the outer side of the gold film away from the optical fiber. The arrangement order of the two thin films cannot be interchanged. The outer palladium film is directly exposed to the electrolyte environment of the power battery 6, and can undergo an adsorption reaction with the hydrogen atoms generated by the electrolyte, causing a decrease in the reflectivity of the palladium film. The inner gold film is arranged on the end face of the optical fiber to improve the overall light reflection intensity of the sensing end face. The two work together to make the end face reflection spectrum carry the hydrogen gas change characteristics. Combined with the temperature and stress optical response brought by the fiber grating 41 and the seven-core optical fiber 42, it is convenient for the spectrometer 5 to calculate three types of physical parameters based on the collected reflection spectrum.

[0036] In some embodiments, the seven-core optical fiber 42 includes a central core and six peripheral cores. The spacing between the cores in the seven-core optical fiber 42 is 10–12 μm, the diameter of the central core and the six peripheral cores is 8–10 μm, and the six peripheral cores are arranged in a hexagonal symmetrical manner.

[0037] It is understandable that the seven-core fiber 42 is composed of a single central core and six peripheral cores arranged in a hexagonal symmetrical pattern, with the spacing between each core controlled at 10–12 μm. The diameter of the central core and the six peripheral cores is uniformly set at 8–10 μm. This standardized size parameter and symmetrical arrangement structure allows the light field transmitted by the central core and peripheral cores to achieve efficient and stable coupling, successfully exciting supermodes with different refractive indices and generating characteristic interference spectra. This makes the wavelength drift caused by temperature and stress stable and controllable. Combined with the amplitude modulation effect of the palladium composite film 43 on the end face, it ensures that the optical signals corresponding to the three physical quantities do not interfere with each other.

[0038] In some embodiments, the fiber grating 41 is a single-mode fiber, and the single-mode fiber is aligned with the central fiber core.

[0039] It is understandable that the single-mode fiber, which serves as the carrier of the fiber grating 41, is precisely aligned and assembled with the central core of the seven-core fiber 42, without the need to match the other six peripheral cores. This alignment method can constrain the incident light to couple only into the central core, stably generating two supermodes and forming a characteristic interference spectrum inside the seven-core fiber 42. This enables the orthogonal separation of the optical signals corresponding to temperature, stress, and hydrogen, providing structural support for the subsequent accurate calculation of the three internal physical parameters of the power battery 6 based on the reflection spectrum.

[0040] In some embodiments, the multi-parameter fiber optic sensor 4 further includes an insulating encapsulation layer 44, which encapsulates the fiber optic grating 41 and the seven-core fiber 42, and leaves an exposure window for the palladium composite film 43 at the second end of the seven-core fiber 42.

[0041] The insulating encapsulation layer 44 can be made of polyimide material that is compatible with the electrolyte environment.

[0042] It is understandable that by using an insulating encapsulation layer 44 to cover and encapsulate the main structure of the fiber optic grating 41 and the seven-core optical fiber 42, the corrosive electrolyte inside the power battery 6 can be isolated, preventing the optical fiber body from being corroded and damaged by the electrochemical medium and preventing stray media from interfering with the optical fiber transmission. At the same time, only a window is reserved at the end of the device to expose the palladium-gold composite film 43, ensuring that the outer palladium film can directly contact the hydrogen atoms in the electrolyte to undergo an adsorption reaction, thus fully preserving the hydrogen sensing function while achieving long-term stable operation of the sensor.

[0043] Based on the above embodiments, the fabrication process of the multi-parameter fiber optic sensor 4 in the application can be as follows: a section of seven-core fiber 42 is cut and fused to a single-mode fiber with a fiber grating 41 in a central core alignment manner. Then, the end of the seven-core fiber 42 is cut to process a flat single-reflection end face. Then, the fiber end face is vertically placed into a magnetron sputtering cavity. With the help of a quartz crystal microbalance for precise thickness control, a gold film of about 10nm is first sputtered and deposited on the end face. Then, a palladium film is deposited on the outside of the gold film through the same sputtering process. Combined, a palladium-gold composite film 43 that can reversibly adsorb hydrogen is formed. Finally, polyimide is used to insulate and encapsulate the fiber grating 41 and the seven-core fiber 42 as a whole, leaving only the end face composite film exposed as a sensitive window.

[0044] Based on this, the embedded installation process of the power battery 6 can be as follows: mix active materials, conductive agents and binders to prepare electrode slurry, and coat it on the surfaces of copper and aluminum current collectors respectively. Then, prepare positive and negative electrode sheets by drying, rolling and cutting processes in sequence; the positive and negative electrode sheets are wound together with the separator to form the battery cell. During the assembly stage, the encapsulated fiber optic sensor parallel electrode sheet is pre-embedded between the separator and the negative electrode sheet to ensure that the sensitive end face is close to the electrolyte and electrode interface; when the battery cell aluminum-plastic film is heat-sealed and formed, epoxy resin is used to seal and insulate the fiber optic lead outlet.

[0045] In some embodiments, the spectrometer 5 is also used to acquire amplitude data and wavelength drift data at the target wavelength in the reflection spectrum, and to determine the temperature, stress and hydrogen concentration at the measurement interface of the power battery 6 based on the amplitude data and wavelength drift data at the target wavelength, wherein the wavelength range of the target wavelength is 1550-1600nm.

[0046] For example, the target wavelength can be 1578nm.

[0047] In the application, the inherent operating band of polarization controller 2 and circulator is 1550±50nm. Based on this, the spectrometer 5 selects 1550-1600nm as the target wavelength acquisition range, which can ensure the normal operation of the entire optical path device and prevent optical signal loss and distortion caused by exceeding the operating frequency band. On the other hand, this range contains the characteristic peak position of 1578nm. The interference peak at this position has the highest amplitude response sensitivity to the change in refractive index compared with other spectral peaks in the same band. Selecting data acquisition in this range can maximize the signal acquisition accuracy, reduce the data interference caused by other low-sensitivity spectral peaks, and ensure the accuracy and reliability of the subsequent three physical parameter calculation results.

[0048] In some embodiments, please refer to Figure 3 This application provides a method for monitoring multiple physical quantities inside a power battery. The method for monitoring multiple physical quantities inside a power battery is performed based on a fiber optic sensing device for multiple physical quantities inside a power battery as described above. The method for monitoring multiple physical quantities inside a power battery includes the following steps S301 to S303.

[0049] S301: Preprocess the reflection spectrum to extract wavelength data at the target wavelength. The wavelength data includes the overall wavelength drift data of the seven-core fiber supermode interference spectrum, the wavelength drift data of the Bragg reflection peak, and the amplitude data at the target wavelength.

[0050] S302: Obtain the 3×3 sensitivity matrix calibrated under standard operating conditions, where the standard operating conditions are constant temperature, no strain, and no hydrogen environment.

[0051] S303: The measurement temperature is determined based on the overall wavelength drift data of the 3×3 sensitivity matrix, baseline temperature, and seven-core fiber supermode interference spectrum; the measurement strain is determined based on the wavelength drift data of the 3×3 sensitivity matrix, baseline strain, and Bragg reflection peak; and the measurement hydrogen concentration is determined based on the 3×3 sensitivity matrix, baseline hydrogen concentration, and amplitude data at the target wavelength.

[0052] The spectrometer acquires the reflection interference spectrum in real time, and after smoothing and normalization, extracts three independent observations: the overall wavelength drift of the seven-core fiber supermode interference spectrum. Wavelength shift of the Bragg reflection peak The normalized amplitude variation ΔA at a specific wavelength in the fiber grating interference spectrum. In this embodiment, the steady-state value under normal battery cycling is used as a reference baseline, and the actual parameters are calculated in real time. ,in, To measure temperature, The change in temperature Baseline temperature To measure strain, The change in strain Baseline temperature To measure hydrogen concentration, This represents the change in hydrogen concentration. The baseline concentration change is used to suppress noise by applying a low-pass filter, and the heating rate dT / dt, strain rate dε / dt, and H2 generation rate d[H2] / dt are calculated.

[0053] Observation vector: The vector being measured: 3×3 sensitivity matrix K: , .

[0054] The temperature decoupling formula is:

[0055] The strain decoupling formula is:

[0056] The hydrogen concentration decoupling formula is:

[0057] It should be noted that the method for monitoring multiple physical quantities inside a power battery provided in this application embodiment and the fiber optic sensing device for multiple physical quantities inside a power battery provided in this application embodiment are based on the same inventive concept. Therefore, the specific implementation of this embodiment can refer to the implementation of the aforementioned fiber optic sensing device for multiple physical quantities inside a power battery, and the repeated parts will not be described again.

[0058] In some embodiments, the method for monitoring multiple physical quantities inside a power battery further includes: calibrating a temperature reference value, a strain reference value, and a hydrogen concentration reference value for normal battery operation as baseline temperature, baseline strain, and baseline hydrogen concentration, respectively; determining the deviation of the measured temperature, measured stress, and measured hydrogen concentration from the corresponding reference values; determining the anomaly level of each physical quantity based on each deviation; and determining the thermal runaway risk level of the measured power battery based on the anomaly level of each physical quantity.

[0059] After obtaining the three independent parameters from the real-time decoupled output of the sensor, a multi-parameter fusion evaluation algorithm is used to comprehensively characterize the "electrochemical-thermal-mechanical-gas" coupling state of the high-power lithium battery and realize graded early warning of thermal runaway. The evaluation and early warning process consists of three steps: parameter preprocessing and baseline calibration, threshold definition and multi-level graded evaluation logic.

[0060] Threshold definitions: calibrated through overcharge / overheating / abuse experiments and set with reference to existing literature: Hydrogen concentration [H2]: Slight anomaly: 50–200 ppm or generation rate >10 ppm / min; High risk: >500 ppm. Temperature ΔT: Slight anomaly: ΔT >2–5 °C or dT / dt >5 °C / min; High risk: ΔT >10 °C or dT / dt >10 °C / s. Strain / stress Δε: Slight anomaly: Δε >100–500 με; High risk: Δε >1000 με or dε / dt >50 με / s. See Table 1 below for details.

[0061] Table 1 shows the multi-level hierarchical evaluation logic.

[0062] This early warning mechanism adopts a hierarchical assessment logic of "gas sensitivity priority and multi-parameter coordination". Under normal conditions, internal temperature, strain, and hydrogen concentration are all maintained within the dynamic baseline. When an early anomaly occurs, the system enters a mild early warning state. At this time, the absolute leading effect of the gas is given priority. Only a specific rise in H2 (>10 ppm) accompanied by a slight temperature rise (70°C -90°C) is needed to indicate the initial decomposition of the negative electrode SEI film, thus providing the system with the earliest possible treatment window. As the reaction deteriorates and enters the intermediate-risk state, H2 rises rapidly (>100 ppm) and the temperature enters the accelerated heat generation zone (90°C - 130°C), marking the full-scale start of oxygen release from the high-nickel positive electrode and irreversible side reactions. When approaching the high-risk state, if any two or more parameters reach their limits (e.g., temperature ≥140°C, H2>1000 ppm), it means that a large-area internal short circuit and fire risk are imminent, and emergency physical shutdown must be implemented immediately. In addition, the system has a strain veto mechanism: regardless of the status of other parameters, once the optical fiber detects an irreversible mechanical strain mutation that far exceeds the normal phase transition expansion (such as instantaneously exceeding the 3000 µε threshold or a cliff-like drop caused by the rupture of the aluminum-plastic film), it will directly trigger a high-risk alarm.

[0063] In some embodiments, an electronic device provided in this application includes a processor and a memory; the memory stores a computer program, wherein the computer program, when executed by the processor, implements the above-described method for monitoring multiple physical quantities inside a power battery.

[0064] Specifically, the processor may include, for example, a general-purpose microprocessor, an instruction set processor and / or an associated chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor may also include onboard memory for caching purposes. The processor may be a single processing unit or multiple processing units for performing different actions of the method flow according to embodiments of this application.

[0065] Memory can be any medium capable of containing, storing, transmitting, propagating, or transmitting instructions. For example, memory can include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, instruments, or propagation media. Specific examples of memory include: magnetic storage devices such as magnetic tape or hard disk drives (HDDs); optical storage devices such as optical discs (CD-ROMs); and also random access memory (RAM) or flash memory; and / or wired / wireless communication links.

[0066] This application also provides a non-transitory computer storage medium storing a computer program thereon. When executed by a processor, this program implements the aforementioned method for monitoring multiple physical quantities inside a power battery. This computer-readable medium may be included in the device / apparatus / system described in the above embodiments; or it may exist independently and not assembled into that device / apparatus / system. The aforementioned computer-readable medium carries one or more programs, which, when executed, implement the method as described in the embodiments of this application.

[0067] According to embodiments of this application, a computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this application, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this application, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media can also be any computer-readable medium other than computer-readable storage media, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wired, optical fiber, radio frequency signals, etc., or any suitable combination thereof.

[0068] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0069] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application, even if such combinations or combinations are not explicitly described in this application. All such combinations and / or combinations fall within the scope of this application. Therefore, the scope of this application should not be limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A fiber optic sensing device for multiple physical quantities inside a power battery, characterized in that, include: Light source, polarization controller, fiber optic circulator, multi-parameter fiber optic sensor, and spectrometer; The light source is used to output initial light to the polarization controller; The polarization controller is used to convert the initial light into linearly polarized light at a preset angle and transmit the linearly polarized light to the first port of the fiber optic circulator; The second port of the fiber optic circulator is connected to the multi-parameter fiber optic sensor, and the third port of the fiber optic circulator is connected to the spectrometer. The fiber optic circulator is used to transmit the linearly polarized light unidirectionally from the first port to the second port, and to transmit the interference signal light reflected back by the multi-parameter fiber optic sensor unidirectionally from the second port to the third port. The multi-parameter fiber optic sensor includes a fiber optic grating and a seven-core fiber. The first end of the fiber optic grating is connected to the second port. The first end of the seven-core fiber is fused to the second end of the fiber optic grating. A palladium-gold composite film is disposed on the end face of the second end of the seven-core fiber. The end face of the second end of the seven-core fiber is immersed in the medium to be measured. The spectrometer is used to collect the reflection spectrum based on the interference signal light, and to determine the measurement temperature, measurement stress, and measurement hydrogen concentration at the power battery measurement interface based on the reflection spectrum.

2. The fiber optic sensing device for multiple physical quantities inside a power battery as described in claim 1, characterized in that, The palladium-gold composite film comprises: a gold film layer and a palladium film layer stacked together; The gold film layer is located on the end face of the second end of the seven-core optical fiber, and the palladium film layer is located on the side of the gold film layer away from the seven-core optical fiber.

3. The fiber optic sensing device for multiple physical quantities inside a power battery as described in claim 2, characterized in that, The thickness of the gold film layer ranges from 10 to 12 nm, and the thickness of the palladium film layer ranges from 8 to 15 nm.

4. The fiber optic sensing device for multiple physical quantities inside a power battery as described in claim 1, characterized in that, The seven-core optical fiber includes a central core and six peripheral cores. The spacing between the cores in the seven-core optical fiber is 10–12 μm, and the diameter of the central core and the six peripheral cores is 8–10 μm. The six peripheral cores are arranged in a hexagonal symmetrical pattern.

5. The fiber optic sensing device for multiple physical quantities inside a power battery as described in claim 4, characterized in that, The fiber grating is a single-mode fiber, and the single-mode fiber is aligned with the central fiber core.

6. The fiber optic sensing device for multiple physical quantities inside a power battery as described in claim 1, characterized in that, The multi-parameter fiber optic sensor further includes an insulating encapsulation layer, which is used to encapsulate the fiber grating and the seven-core fiber, and leaves an exposure window for the palladium composite film at the second end of the seven-core fiber.

7. The fiber optic sensing device for multiple physical quantities inside a power battery as described in claim 1, characterized in that, The spectrometer is also used to collect amplitude data and wavelength drift data at the target wavelength in the reflection spectrum, and to determine the temperature, stress and hydrogen concentration at the power battery measurement interface based on the amplitude data and wavelength drift data at the target wavelength, wherein the wavelength range of the target wavelength is 1550-1600nm.

8. The fiber optic sensing device for multiple physical quantities inside a power battery as described in any one of claims 1 to 7, characterized in that, The second end face of the seven-core optical fiber is a single-reflection end face.

9. A method for monitoring multiple physical quantities inside a power battery, characterized in that, The method for monitoring multiple physical quantities inside a power battery is performed based on the fiber optic sensing device for multiple physical quantities inside a power battery as described in any one of claims 1 to 8; the method for monitoring multiple physical quantities inside a power battery includes: The reflection spectrum is preprocessed to extract wavelength data at the target wavelength. The wavelength data includes the overall wavelength drift data of the seven-core fiber supermode interference spectrum, the wavelength drift data of the Bragg reflection peak, and the amplitude data at the target wavelength. Obtain the 3×3 sensitivity matrix calibrated under standard operating conditions, wherein the standard operating conditions are constant temperature, no strain, and hydrogen-free environment. The measurement temperature is determined based on the 3×3 sensitivity matrix, baseline temperature, and overall wavelength drift data of the seven-core fiber supermode interferometry spectrum. The measurement strain is determined based on the 3×3 sensitivity matrix, baseline strain, and wavelength drift data of the Bragg reflection peak. The measurement hydrogen concentration is determined based on the 3×3 sensitivity matrix, baseline hydrogen concentration, and amplitude data at the target wavelength.

10. The method for monitoring multiple physical quantities inside a power battery as described in claim 9, characterized in that, The method for monitoring multiple physical quantities inside the power battery also includes: The temperature reference value, strain reference value, and hydrogen concentration reference value used to calibrate the normal operation of the battery are respectively used as the baseline temperature, baseline strain, and baseline hydrogen concentration; Determine the deviations of the measured temperature, the measured stress, and the measured hydrogen concentration from the corresponding reference values; The anomaly level of each physical quantity is determined based on the deviation, and the thermal runaway risk level of the measured power battery is determined based on the anomaly level of each physical quantity.

Images